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Questions and Answers
The prechordal plate is primarily derived from the hypoblast layer, which remains its sole contributor throughout the entirety of gastrulation.
The prechordal plate is primarily derived from the hypoblast layer, which remains its sole contributor throughout the entirety of gastrulation.
False (B)
The oropharyngeal membrane, at its formation, strictly incorporates mesodermal elements that are crucial for its structural integrity and subsequent rupture.
The oropharyngeal membrane, at its formation, strictly incorporates mesodermal elements that are crucial for its structural integrity and subsequent rupture.
False (B)
The definitive prechordal mesoderm solely arises from somitic mesoderm, which migrates cranially to populate the region between the epiblast and hypoblast.
The definitive prechordal mesoderm solely arises from somitic mesoderm, which migrates cranially to populate the region between the epiblast and hypoblast.
False (B)
The hypoblast cells that constitute the initial prechordal plate are indistinguishable, morphologically, from the cuboidal cells found ubiquitously throughout the rest of the hypoblast layer.
The hypoblast cells that constitute the initial prechordal plate are indistinguishable, morphologically, from the cuboidal cells found ubiquitously throughout the rest of the hypoblast layer.
The prechordal plate, once fully developed, is rigidly fixed in its anatomical location and does not undergo any substantial displacement throughout the remainder of embryonic development.
The prechordal plate, once fully developed, is rigidly fixed in its anatomical location and does not undergo any substantial displacement throughout the remainder of embryonic development.
The prechordal plate exclusively induces the formation of the midbrain within the neural ectoderm through direct cell-cell signaling.
The prechordal plate exclusively induces the formation of the midbrain within the neural ectoderm through direct cell-cell signaling.
Neural crest cells exclusively populate the prechordal plate, contributing to the formation of the definitive oropharyngeal membrane, effectively isolating it from signals produced by the prechordal mesoderm.
Neural crest cells exclusively populate the prechordal plate, contributing to the formation of the definitive oropharyngeal membrane, effectively isolating it from signals produced by the prechordal mesoderm.
The prechordal plate's influence on forebrain development is entirely dependent on the action of Shh ligands at later stages of the development of the telencephalon
The prechordal plate's influence on forebrain development is entirely dependent on the action of Shh ligands at later stages of the development of the telencephalon
The cloacal membrane, unlike the oropharyngeal membrane, consistently contains a significant amount of intervening mesoderm throughout its entire existence.
The cloacal membrane, unlike the oropharyngeal membrane, consistently contains a significant amount of intervening mesoderm throughout its entire existence.
The transient prechordal plate is crucial for establishing the anterior-posterior axis, operating independently of any influence from the primitive node or streak.
The transient prechordal plate is crucial for establishing the anterior-posterior axis, operating independently of any influence from the primitive node or streak.
Subsequent to gastrulation, the prechordal mesoderm contributes extensively to the formation of the vertebral column.
Subsequent to gastrulation, the prechordal mesoderm contributes extensively to the formation of the vertebral column.
The disruption of prechordal plate formation during embryogenesis solely results in minor craniofacial abnormalities, without impacting overall brain development.
The disruption of prechordal plate formation during embryogenesis solely results in minor craniofacial abnormalities, without impacting overall brain development.
The oropharyngeal membrane is positioned caudally relative to the cranial tip of the developing notochord.
The oropharyngeal membrane is positioned caudally relative to the cranial tip of the developing notochord.
The formation of the prechordal plate is entirely dependent upon the expression of HOX genes.
The formation of the prechordal plate is entirely dependent upon the expression of HOX genes.
The prechordal plate is derived from the splanchnic mesoderm.
The prechordal plate is derived from the splanchnic mesoderm.
The primitive groove extends cranially, ending in the epiblast at the primitive pit.
The primitive groove extends cranially, ending in the epiblast at the primitive pit.
The prechordal mesoderm lies cranial to the notochord, at the cranial tip of the neural tube.
The prechordal mesoderm lies cranial to the notochord, at the cranial tip of the neural tube.
The buccopharyngeal membrane is another name for the oropharyngeal membrane.
The buccopharyngeal membrane is another name for the oropharyngeal membrane.
The prechordal plate is referred to as a mesendodermal structure because of the contribution of mesoderm and endoderm after the cellular migrations.
The prechordal plate is referred to as a mesendodermal structure because of the contribution of mesoderm and endoderm after the cellular migrations.
The oropharyngeal membrane is formed by the tight adhesion of the epiblast and hypoblast layers.
The oropharyngeal membrane is formed by the tight adhesion of the epiblast and hypoblast layers.
Flashcards
Epiblast Layer
Epiblast Layer
Ectodermal layer visible from the embryo's top view during the third week.
Primitive Node
Primitive Node
A swelling containing the primitive pit, present in the early embryo.
Primitive Groove
Primitive Groove
Midline depression extending cranially from the primitive node.
Oropharyngeal Membrane
Oropharyngeal Membrane
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Hypoblast Layer
Hypoblast Layer
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Prechordal Plate
Prechordal Plate
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Forebrain Induction
Forebrain Induction
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Prechordal Plate Formation
Prechordal Plate Formation
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Prechordal Mesoderm
Prechordal Mesoderm
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Cloacal Membrane
Cloacal Membrane
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Prechordal Plate Structure
Prechordal Plate Structure
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Study Notes
Prechordal Plate Overview
- The prechordal plate is a structure in the early embryo often misunderstood.
- The lecture aims to simplify the understanding of the prechordal plate, focusing on its development and function.
Early Embryonic Structures (Start of Third Week)
- The epiblast layer, also known as the ectodermal layer, is visible from a top view of the embryo.
- The primitive node, a swelling, is present, and it contains a circular depression called the primitive pit.
- The primitive streak includes a midline depression known as the primitive groove which extends cranially with primitive pit.
- The primordium of the future baby's mouth, called the oropharyngeal membrane, is present in the ectoderm as a circular depression.
- Some authors refer to the oropharyngeal membrane as the buccopharyngeal membrane.
- The hypoblast layer, also known as the endodermal layer, is located on the underside of the embryo.
- The epiblast and hypoblast layers are tightly adherent at the location of the oropharyngeal membrane.
Defining the Prechordal Plate
- The prechordal plate is the hypoblastic part of the oropharyngeal membrane.
- It is the primitive endodermal component of the oropharyngeal membrane.
- During gastrulation, ground substance is laid down between the hypoblast and epiblast layers, except at the oropharyngeal membrane.
- Consequently, there is very little to no mesoderm between the two layers at the site of the oropharyngeal membrane
Development of the Prechordal Plate
- Epiblast cells proliferate and migrate from the primitive pit towards the prechordal plate.
- These migrating cells intercalate into the prechordal plate, displacing the original hypoblast cells.
- The prechordal plate is then formed by the epiblast-derived cells.
- The oropharyngeal membrane remains a bilaminar structure despite the cellular displacement.
- The hypoblast is replaced in its entirety by the cells originating from the epiblast as gastrulation progresses.
- The cells at the caudal end of the prechordal plate proliferate and differentiate into the prechordal mesoderm in-between the two layers
- At the caudal end, the structure becomes trilaminar, while the cranial end remains bilaminar.
- The prechordal plate is referred to as a mesendodermal structure.The prechordal plate is called mesoendodermal because it originates from early epiblast cells during gastrulation that give rise to both mesodermal and endodermal derivatives, and it exhibits molecular and functional traits of both germ laye
- Neural crest cells enrich the prechordal mesoderm during neural crest cell development.
- The prechordal mesoderm contributes to the formation of mesodermal derivatives of the head.
- The actual oropharyngeal membrane is restricted to the cranial bilaminar end.
- The oropharyngeal membrane will later rupture to form the mouth opening.
Functions of the Prechordal Plate
- The cranial part of the prechordal plate forms the endodermal part of the oropharyngeal membrane.
- The prechordal plate induces the forebrain in the neural ectoderm.
- The prechordal plate forms the prechordal mesoderm, which forms the mesodermal derivatives of the head.
- The prechordal plate lies cranial to the notochord, with the prechordal mesoderm located at the cranial tip of the notochord.
Additional Membrane: Cloacal Membrane
- The cloacal membrane is another bilaminar structure similar to the oropharyngeal membrane.
- There is connection of the ecto- and endodermal layers, with no interspersed mesoderm.
- It will form the opening of the urogenital system and the anus.
Review of Prechordal Plate Development
- Initially, the prechordal plate forms the endodermal layer of the oropharyngeal membrane.
- The prechordal plate consists of tall columnar hypoblast cells.
- The rest of the hypoblast cells are cuboidal while prechordal plate hypoblast cells are specially thickened
- As gastrulation proceeds, the hypoblast is displaced laterally to the yolk sac endoderm.
- New cells from the primitive streak displace the prechordal plate cells laterally.
- The prechordal plate is now formed from cells that ingressed downward from the primitive pit, while the oropharyngeal membrane remains bilaminar.
- The cells at the caudal end of the prechordal plate proliferate and differentiate to form the prechordal mesoderm.
- The cranial part becomes the definitive oropharyngeal membrane.
- The prechordal plate is initially a bilaminar structure and then forms the prechordal mesoderm in between the two layers.
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